DE2948555A1 - Light sensitive mixt. contg. polyurethane resin - from isocyanate prepolymer and poly:ol and diazonium salt polycondensate for negative working printing plate - Google Patents

Abstract

Polyurethane resin (I) used as binder in a light-sensitive mixt., contg. a light-sensitive diazonium salt polycondensation prod. (II), is a reaction prod. of a (branched) polyurethane prepolymer (III) with terminal free NCO gps. and a cpd. (IV) with min. 3 OH gps. in the mol. Pref. (I) has mol.wt. of under 1500 and is the reaction prod. of (III) and 1 mole (IV) per equiv. NCO gp. in (III). (IV) is an at least trihydric aliphatic alcohol. The mixt. contains 0.5-4 (wt.) pts. (I)/pt.(II). Compsn. is negative working and is useful for making printing plates. It can be developed more easily and reliably than the usual mixts.

Description

Photosensitive mixture

The invention relates to a negative working photosensitive Mixture which, as a photosensitive compound, is a diazonium salt polycondensation product and contains a polyurethane resin as a binder and is preferably used for production used by printing plates.

Mixtures of the specified genus are described in US Pat. No. 3,660,097. There are linear polyurethane resins in combination with negative or positive working Diazo compounds described. The mixtures described there and those produced with them Photosensitive copying materials have certain disadvantages. They are in usual Coating solvents, such as glycol monoethers, are relatively poorly soluble Solution must be filtered several times to remove residues. The layers are difficult to develop and the number of copies that can be produced is limited.

From DE-OS 27 39 774 are corresponding mixtures and copying materials known, the polyurethanes with terminal NCO groups in combination with acid included as a stabilizer. These materials have a much better solubility and result in higher print runs.

Their developability is also improved, but not yet optimal.

The object of the invention was to provide photosensitive mixtures of the specified To propose genus that are easier and safer to develop than the known Mixtures.

The invention is a photosensitive mixture that as photosensitive compound a diazonium salt polycondensation product and as Binder contains a polyurethane resin.

The mixture according to the invention is characterized in that the polyurethane resin a reaction product of a free-terminated polyurethane prepolymer NCO groups and a compound with at least three hydroxyl groups in the molecule.

Preferred prepolymers with terminal 14CO groups are those are used which contain more than two NCO groups in the molecule, ie are branched. Such branched prepolymers are named and commercially available and are manufactured by reacting diisocyanates with hydroxy compounds, at least a portion of which contains three or more than three hydroxyl groups in the molecule.

The polyurethane resins contained in the photosensitive mixture preferably have a molecular weight below 1500, in particular between 700 and 1200.

Suitable prepolymers with terminal free NCO groups are in DE-OS 27 39 774 described.

As compounds with at least three hydroxyl groups in the molecule can aromatic and aliphatic hydroxy compounds can be used. Aliphatic Connections are preferred. Un is the molecular weight of the reaction product not to increase too much, low molecular weight alcohols with 3 to 10, in particular 3 to 6 hydroxyl groups are preferred. Examples of suitable hydroxy compounds are Glycerine, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, sorbitol, Mannitol, pyrogallol, phloroglucine and trihydroxybenzophenone. Glycerin becomes special preferred.

In the manufacture of the hydroxyl-terminated polyurethane resin the hydroxy compound must be added at least in such an amount that all NCO groups are implemented. To the formation of less desirable high molecular weight To avoid reaction products, the hydroxy compound is preferably used in excess, expediently in an amount of about 0.8 to 1.2 mol of hydroxy compound per 1 equivalent NCO groups, used. A ratio of 1 mole of the hydroxy compound is particularly preferred 1 equivalent of NCO each.

The quantitative ratio between the polyurethane resin and the diazonium salt polycondensation product is generally between 0.5 and 4, preferably between 1 and 3, parts by weight Resin per 1 part by weight of diazonium compound.

The diazonium salt polycondensation products are condensation products condensable aromatic diazonium salts, e.g. B. of diphenylamine-4-diazoniunisalzen, with aldehydes, preferably formaldehyde, suitable. Mixed condensation products are particularly advantageous used, those other than the diazonium salt units do not contain light-sensitive units that are caused by condensable compounds, in particular aromatic amines, phenols, phenol ethers, aromatic thioethers, aromatic hydrocarbons, aromatic heterocycles and organic acid amides, are derived.

These condensation products are described in DE-OS 20 24 244. In general, all diazonium salt polycondensation products are suitable in the DE-OS 27 39 774 are described.

The mixtures according to the invention can except diazo compounds and Polyurethane resins other common ingredients, such as dyes, pigments, acids, Contains plasticizers, adhesion promoters and other resins in small quantities.

The mixtures can be used for the production of relief images, photoresists, Color proofing foils, screen printing stencils and printing plates for relief, gravure and flat printing be used. They are preferred for the production of planographic printing plates, in particular presensitized planographic printing plates.

For this purpose, they are applied to suitable substrates, e.g. B. on Magnesium, zinc, copper, aluminum, steel, multi-metal plate, plastic films, metal or polyamide screens. Aluminum, the surface of which is known, is particularly preferred Way mechanically, chemically or electrolytically roughened, if necessary anodized and / or pretreated with silicate or polyvinylphosphonic acid solutions can be.

The processing of the copy materials obtained from the mixtures takes place in a known manner by imagewise exposure and washing out of the unexposed Layer areas with a suitable developer. As a developer are preferred aqueous solutions used which contain at least 80 wt .-% water. Suitable Developer solutions are described in DE-OS 28 09 774.

After developing, the materials can be used immediately, z. B. as letterpress forms. You can also apply heat treatment in a known manner of a few minutes at around 200-2400C to complete the print run raise.

The mixtures according to the invention produce light-sensitive copier layers, which are particularly easy and clean with environmentally friendly aqueous developer solutions let develop.

The following examples illustrate preferred embodiments of the Invention. Percentages and ratios are to be understood in weight units.

Example 1 An electrolytically roughened and anodically oxidized Aluminum foil was at a temperature of 70-900C in a 0.1% aqueous solution dipped in polyvinylphosphonic acid, then rinsed with water and dried. on the substrate thus pretreated became a solution of the following ingredients Applied in such a thickness that, after drying, a layer weight of 1 g / m2 the following was obtained: 3.00 pbw of the polyurethane resin described below, 1.56 pbw of the condensation product from 1 mole of 3-methoxydiphenylamine-4-diazonium salt and 1 mole of 4,4'-bis-methoxymethyl-diphenyl ether, isolated as mesitylene sulfonate, 0.04 pbw metanil gel (C.I. 13065), 0.1 pbw phosphoric acid (85%), 2.00 pbw of a pigment dispersion of 10% bronze blue R (C.I. 42765: 1), 20 % of the polyurethane resin given below and 70% ethylene glycol methyl ether acetate, 93.30 pbw of ethylene glycol monomethyl ether.

The obtained photosensitive planographic printing plate was placed under a Original exposed for 40 seconds with a 5 kW metal halide lamp at a distance of 130 cm. The exposed layer was wiped with the following developer solution developed a plush tampon: 85.47 pbw water, 3.42 pbw polyvinyl alcohol (12% residual acetyl groups, K value 4), 2; 56 pbw benzyl alcohol, 2.56 pbw glycerol triacetate, 2.56 pbw of ammonium alkyl polyoxyethylene sulfate (alkyl group with 18 carbon atoms), 2.56 pbw Na2S04 ~ 10 H20, 0.85 pbw gelatin and 0.03 pbw hydroquinone.

The printing form obtained was rinsed with water and wiped off with a doctor blade. she delivered over 100,000 prints in a standard offset printing machine.

The polyurethane resin used was prepared as follows: 83 g glycerine were mixed with 100 ml of ethylene glycol monoethyl ether. Into the mixture was at Room temperature a solution of 65 g of the reaction product containing isocyanate groups from 1 mole of trimethylolpropane and 3 moles of tolylene diisocyanate in 50 ml of ethylene glycol monomethyl ether dripped in. After everything was added dropwise, the temperature was increased and 4 hours kept at around 800C. After cooling, the reaction mixture slowly became in Pour 2 liters of 5% sodium chloride solution. The fancy brownish white one Precipitate was filtered off and carefully dried. The powdery resin was used directly in the coating solution.

Example 2 A solution of 3.00 pbw of that prepared analogously to Example 1 Reaction product of 3 moles of pentaerythritol and 1 bbl of the isocyanate groups specified there containing reaction product, 1.75 pbw of the diazonium salt polycondensate specified in Example 1, 1.50 pbw of a pigment dispersion of 15% real green GG (C.I. 74260), 15% of the above specified reaction product and 70% ethylene glycol methyl ether acetate, 0.10 pbw phosphoric acid (85%) and 0.04 pbw of metanil yellow in 93.50 pbw of ethylene glycol monomethyl ether was added applied the support given in the example in such a way that a dry layer weight of 0.9 g / m2 was obtained.

The printing plate obtained was exposed and developed as in Example 1 and delivered an edition of 50,000 prints.

Example 3 A coating solution was prepared as in Example 2, however, the polyurethane resin was replaced by the equal amount of the reaction product from 3 ttol sorbitol and 1 mol of the reaction product containing isocyanate groups replaced. The processing was carried out as in Example The photosensitive obtained After exposure, the planographic printing plate could be developed without leaving any residue 50,000 prints.

Example 4 A solution of 3/60 pbw of that described in Example 1 Polyurethane resin, 0.90 pbw of the diazonium compound given in Example 1, 2.00 Pbw of the pigment dispersion given in Example 1, 0.04 pbw metanil yellow and 0.10 pbw Pbw phosphoric acid (85%) in 93.30 pbw ethylene glycol monomethyl ether becomes a dry layer weight of 0.7 g / m2 applied to the substrate specified in Example 1.

The plate was placed under a negative original for 30 seconds with the in Example 1 exposed light source and then exposed within 60 seconds in a commercially available continuous developing machine with the one specified in Example 1 Developer developed.

The printing form obtained produced 50,000 in an offset printing machine excellent prints.

Even after a storage time of 4 weeks, the presensitized plate could be used just as easy to process.

Example 5 A presensitized offset printing plate was prepared as in Example 4 produced, but with the exception that the polyurethane used there by the same amount of the reaction product from 3 moles of 2,3,4-trihydroxy-benzophenone and 1 plol of the reaction product containing isocyanate groups indicated in Example 1 was replaced. Results similar to those in Example 4 are obtained.

Example 6 A presensitized offset printing plate was prepared as in Example 1 described, but an aluminum foil was used as the support used, the surface of which is roughened by brushing with a pumice stone suspension had been. The layer thickness of the light-sensitive layer was 0.9 / m2. It was 60 seconds exposed under the conditions given in Example 1 and as there developed. The printing form obtained produced 50,000 prints.

Example 7 As described in Example 1, a presensitized Offset printing plate was produced with a layer weight of 1 g / m2 the diazonium compound indicated there by the same amount of the condensation product from diphenylamine-4-diazonium salt and paraformaldehyde, produced in 85% iter phosphoric acid, replaced. The printing plate was made 160 under the conditions given in Example 1 Seconds exposed and developed as described there. The results were similar obtain.

Example 8 A solution of 3.00 pbw of the polyurethane resin described below, 1.56 pbw of the diazonium compound specified in Example 1, 0.04 pbw metanil yellow, 0.10 pbw of phosphoric acid and 2.00 pbw of the pigment dispersion given in Example 1 in 93.30 pbw of ethylene glycol monomethyl ether was given on the i.l Example 1 Layer base applied in such a way that, after drying, a layer weight of 19 / m2 was obtained.

The printing plate was exposed for 45 seconds as in Example 1 and then as developed there. The results were similar to those of Example 1.

The polyurethane resin used was prepared as follows: A commercially available one Polyurethane prepolymer obtained by reacting about 8 moles of 2,4-tolylene diisocyanate with 1 mol of 1,4-butanediol, 1 mol of polypropylene glycol (MW 1000) and 2 ol l, l, l-trimethylolpropane and containing 7% Preic flCO groups, was made with glycerine in such #! en # e implemented that 1 mole of glycerol came to 1 mole of NCO groups. The implementation was made in the same manner as for the polyurethane resin described in Example 1 carried out.

Claims (6)

Claims @ Photosensitive mixture, which as photosensitive Compound a diazonium salt polycondensation product and a polyurethane resin as a binder contains, characterized in that the polyurethane resin is a reaction product a polyurethane prepolymer with terminal free NCO groups and a compound with at least three hydroxyl groups in the molecule. 2. Photosensitive mixture according to claim 1, characterized in that that the polyurethane resin is made from a branched polyurethane prepolymer has been. 3. Photosensitive mixture according to claim 1, characterized in that that the polyurethane resin has a molecular weight below 1500. 4. Photosensitive mixture according to claim 1, characterized in that that the polyurethane resin is a reaction product of an at least trivalent aliphatic Alcohol is. 5. Photosensitive mixture according to claim 1, characterized in that that there are 0.5 to 4 parts by weight of polyurethane resin per 1 part by weight of diazonium salt polycondensation product contains. 6. Photosensitive mixture according to claim 1, characterized in that that the polyurethane resin is a reaction product of a polyurethane prepolymer and 1 mol of polyvalent hydroxy compound per 1 equivalent of NCO groups in the prepolymer is.